In the manufacture of an electronic device such as a semiconductor device, a plasma processing is performed by using a plasma processing apparatus. For example, a processing such as etching or film formation is performed by exposing a processing target object to plasma.
In a process including the plasma processing, different kinds of plasma processings may be performed on the processing target object by changing gases supplied into a single processing vessel in sequence. To perform this process, the plasma processing apparatus needs to be equipped with a gas supply system capable of supplying different kinds of gases while changing them. As an example of the plasma processing apparatus including such a gas supply system, there is known a plasma processing apparatus described in Patent Document 1.
The plasma processing apparatus disclosed in Patent Document 1 is equipped with a processing vessel and a shower head. The shower head has a multiple number of gas discharging units through which gases are supplied toward different zones within the processing vessel, that is, toward a multiple number of concentric regions on the processing target object. The gases are supplied from the gas supply system into the multiple number of gas discharging units individually.
The gas supply system includes a plurality of flow rate control unit groups. Each flow rate control unit group includes a multiple number of flow rate control units. Each flow rate control unit belonging to the corresponding flow rate control unit group is connected to the corresponding one of the gas discharging units.
Further, the gas supply system is equipped with a multiple number of branch lines through which the gases are distributed to the corresponding flow rate control units of the individual flow rate control unit groups. In addition, the gas supply system has pipelines respectively connected to the multiple number of branch lines. Different kinds of multiple gas sources are connected to each of these pipelines via valves.
In the plasma processing apparatus recited in Patent Document 1, a gas from a gas source selected from the multiple gas sources connected to each pipeline via the valves is distributed into the multiple number of flow rate control unit groups, and the corresponding gas can be then supplied into the multiple number of gas discharging units from the multiple number of flow rate control unit groups. Further, by changing the kind of the gas to be supplied into each pipeline, it is possible to change the kind of the gas to be supplied to the multiple number of gas discharging units. Accordingly, different kinds of plasma processings can be performed on the processing target object within the single processing vessel.
Patent Document 1: Japanese Patent Laid-open Publication No. 2013-051315
In the gas supply system of the plasma processing apparatus described in Patent Document 1, when changing the gas to be supplied into the gas discharging units, it is required to replace the gas within the gas supply system. Since, however, it takes time to replace the gas, the throughput of the process is deteriorated.